Instantly Morton was on his feet and the two were staggering out of the room, into the immense, dusky corridor outside. Down it they ran, for a moment, then suddenly stopped. For from ahead had come the sound of immense steps, while some vast black bulk had suddenly blotted out the great square of crimson light at the corridor's open end, ahead. Then, as it came on, they saw the great thing clearly--a gigantic brontosaur that had halted momentarily a hundred feet down the corridor from them. A moment it surveyed them with small, glaring reptilian eyes, then raised its mighty neck and head with a vast, hoarse bellow and thundered straight down upon them. 6 As the colossal beast charged down upon them Rowan stood motionless, stunned, seeing as though in some nightmare dream the great snaky neck and head, the gigantic, trampling feet, and hearing in his ears the deep bellow of the oncoming monster. Then suddenly Morton had leapt forward, beside him, uttering a high, harsh-voiced cry, a cry at which the thundering brontosaur suddenly slowed, stopped. A scant twenty feet from them it stood, regarding them suspiciously, and Morton turned swiftly to the other. "Come on, Rowan!" he cried. "I heard the lizard-men direct these beasts with that cry--I think it'll hold this one till we get past!" Together they ran forward, down the corridor toward the gigantic brontosaur, which was regarding them with its small eyes in seeming perplexity, its head swaying to and fro on its sinuous neck as they neared it. Now they were to the great beast, pressing past it and between its great body and the corridor wall, its mighty bulk looming above them awe-inspiringly in the great corridor. As they ran past it the huge beast half turned, half stepped toward them, but as Morton repeated his strange high cry it halted again. The next moment Rowan breathed for the first time in seconds, for they were past the brontosaur and racing on down the corridor toward its open end. As they neared that end they slowed their pace, crept forward more cautiously, until they were peering out into the great, crimson-lit street. The broad avenue seemed quite deserted and empty, and they sprang out into it, toward the central plaza where lay the lake of fire and its ascending and descending disk. But suddenly Morton turned, pointed back. Far down the street behind them a great mass of huge figures was moving toward them--a mob of mighty dinosaurs and lizard-riders which was coming rapidly up the avenue. "They're coming now!" cried Morton. "They've gathered--they're ready--they're going to go up the shaft, _now_!"